The purpose of this research is to study the development of emotional self-regulation (ESR) across the second and third years of life and the relations of ESR to parental behavior and infant temperament. ESR refers to the set of processes involved in the initiation and modulation of both positive and negative emotions. ESR is viewed as a developmental phenomenon that should show age-graded movement toward increasingly complex forms, and as a set of individual differences in the ESR strategies deployed and in the effectiveness of these strategies.Two projects are proposed. The first is a cross-sectional study of four age groups (12-to 32-months), that employs three newly developed or adapted observational paradigms for assessing ESR (Separation, Frustration, and Free Play). The first two paradigms will be used to assess ESR strategies for modulating negative emotion, the third to study the initiation of positive affect. Maternal behavior will also be observed in the latter two paradigms and in a structured play paradigm to investigate relations among three theoretically specified components of caretaker sensitivity (autonomy support, provision of structure, and caretaker involvement) and the child ESR measures. A newly developed parent questionnaire will also be used to assess the full set of constructs. Project 2 begins with a home visit at 3 months that includes a videotape-aided assessment of infant temperament. Using the same observational and questionnaire assessments as Project 1, analyses of longitudinal data from 3, 12, 18 and 24 months will focus on intra-individual change in ESR, specifically the prediction of individual differences in ESR "growth curves" by maternal and paternal behavior and temperament measures; and, the testing of alternative models of interrelations among ESR, parent behavior, and temperament over the first two years of life.